Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Turbulence & Mach number. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Axial wave propagation in coupled nanorod system with nonlocal small scale effects

Abstract: This article deals with the axial wave propagation properties of a coupled nanorod system with consideration of small scale effects. The nonlocal elasticity theory has been incorporated into classical rod/bar model to capture unique features of the coupled nanorods under the umbrella of continuum mechanics theory. Nonlocal rod model is developed for coupled nanorods. The strong effect of the nonlocal scale has been obtained which leads to substantially different wave behavior of nanorods from those of macroscopic rods. Explicit expressions are derived for wavenumber, cut-off frequency and escape frequency of nanorods. The analysis shows that the wave characteristics of nanorods are highly over estimated by the classical rod model, which ignores the effect of small-length scale. The studies also shows that the nonlocal scale parameter introduces certain band gap region in axial or longitudinal wave mode, where no wave propagation occurs. This is manifested in the spectrum cures as the region, where the wavenumber tends to infinite or wave speed tends to zero. The effect of the coupled spring stiffness is also capture in the present analysis. It has been also shown that the cut-off frequency increases as the stiffness of the coupled spring increases and also the coupled spring stiffness has no effect on escape frequency of the axial wave mode in the nanorod. This cut-off frequency is also independent of the nonlocal small scale parameter. The present study may bring in helpful insights while investigating multiple-nanorod-system-models for future nano-optomechanical systems applications. The results can also provide useful guidance for the study and design of the next generation of nanodevices that make use of the wave propagation properties of coupled single-walled carbon nanotubes or coupled nanorods. (C) 2011 Elsevier Ltd. All rights reserved.

Liquid-Fueled Strut-Based Scramjet Combustor Design: A Computational Fluid Dynamics Approach

Abstract: Computational-fluid-dynamics-based design and analysis is presented for a full-scale scramjet combustor with kerosene fuel injected from struts placed in the combustor flowpath. Three-dimensional Navier-Stokes equations are solved with a K-e turbulence model using commercial computational-fluid-dynamics software. Combustion is modeled based on infinitely fast chemical kinetics. Lagrangian dispersed-phase analysis is considered for fueldroplet evaporation and mixing in the supersonic stream. Parametric studies are carried out to investigate the effect of combustor-inlet Mach number and total pressure on the flow development process. A higher combustor-entry Mach number and distributed-fuel-injection system will ensure the existence of predominant supersonic flow in the combustor. Simulations are also carried out to investigate two different kinds of fuel injection struts in the scramjet combustor performance. A distributed-fuel -injection system, required to avoid thermal choking, increases the three-dimensionality of the flowfield.

Nonlinear panel flutter by finite-element method

Abstract: Les equations non lineaires sont calculees a partir de considerations energetiques et la force d'etirement non lineaire est formulee en termes de deplacement transversal seul